U.S. patent application number 10/750551 was filed with the patent office on 2005-04-07 for systems and methods for immobilization using selected electrodes.
Invention is credited to Nerheim, Magne H., Smith, Patrick W..
Application Number | 20050073797 10/750551 |
Document ID | / |
Family ID | 34397046 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050073797 |
Kind Code |
A1 |
Smith, Patrick W. ; et
al. |
April 7, 2005 |
Systems and methods for immobilization using selected
electrodes
Abstract
Systems and methods for immobilizing a target such as a human or
animal with a stimulus signal coupled to the target via numerous
electrodes select particular electrodes to use for the stimulus
signal. Subsets of electrodes may be tested by applying a test
signal and monitoring the energy or charge delivered during a
prescribed time. If the delivered energy or charge using a
particular subset of electrodes as indicated by monitoring test
pulse amplitude suitably compares to a limit, then the particular
subset is selected for applying the stimulus signal. A first
stimulus signal may be applied to a first subset of electrodes to
prompt movement of the target toward an electrode that, when better
coupled to the target as a consequence of movement of the target
will provide a more effective subset of electrodes for further
stimulus. For example, a projectile with closely spaced electrodes
may stimulate a burning sensation to attract the target to impale
the target's hand on a rear facing electrode of the projectile. Use
of the rear facing electrode and one or more of the closely spaced
electrodes may provide a more effective stimulus circuit through
tissue of the target.
Inventors: |
Smith, Patrick W.; (Paradise
Valley, AZ) ; Nerheim, Magne H.; (Scottsdale,
AZ) |
Correspondence
Address: |
SQUIRE, SANDERS & DEMPSEY L.L.P.
Two Renaissance Square
Suite 2700
40 North Central Avenue
Phoenix
AZ
85004-4498
US
|
Family ID: |
34397046 |
Appl. No.: |
10/750551 |
Filed: |
December 31, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60509577 |
Oct 7, 2003 |
|
|
|
60509480 |
Oct 8, 2003 |
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Current U.S.
Class: |
361/232 |
Current CPC
Class: |
F42B 12/36 20130101;
F41H 13/0025 20130101 |
Class at
Publication: |
361/232 |
International
Class: |
H02H 001/00 |
Goverment Interests
[0002] The present invention may have been, in part, derived in
connection with U.S. Government sponsored research. Accordingly,
the U.S. Government has a paid-up license in this invention and the
right in limited circumstances to require the patent owner to
license others on reasonable terms as provided for by the terms of
contract No. N00014-02-C-0059 awarded by the Office of Naval
Research.
Claims
What is claimed is:
1. An immobilization device comprising: a first electrode; a second
electrode; a third electrode to come into contact with the target
as a consequence of movement of the target; and a signal generator
selectively coupled to the first electrode, to the second
electrode, and to the third electrode to provide a test signal via
the first electrode and the second electrode to prompt movement of
the target toward the third electrode, and to provide a stimulus
signal for immobilization via the third electrode.
2. The device of claim 1 further comprising: a memory comprising a
list electrodes comprising indicia of the first electrode, the
second electrode, and the third electrode, the list organized by
subset to test; and a processor that directs selective coupling of
listed electrodes to the signal generator in accordance with
monitored energy delivered into the target via the listed
electrodes.
3. The device of claim 1 further comprising: a memory comprising a
list electrodes comprising indicia of the first electrode, the
second electrode, and the third electrode, the list organized by
subset to test; and a processor that directs selective coupling of
listed electrodes to the signal generator in accordance with
monitored charge delivered into the target via the listed
electrodes.
4. The device of claim 1 further comprising: a memory comprising a
list electrodes comprising indicia of the first electrode, the
second electrode, and the third electrode, the list organized by
subset to test; and a processor that directs selective coupling of
listed electrodes to the signal generator in accordance with a
respective impedance between listed electrodes.
5. A method for immobilizing a target, the method comprising: a
step for providing a first electrode in contact with the target and
a second electrode in contact with the target; a step for providing
a first signal via the first electrode and the second electrode; a
step for providing a third electrode for coming into contact with
the target as a consequence of movement of the target in response
to the first signal; and a step for providing an immobilizing
signal via the third electrode.
6. The method of claim 5 wherein the first signal comprises a test
signal.
7. The method of claim 5 wherein the first signal comprises a
stimulus signal.
8. A method for selecting a subset of electrodes from a plurality
of electrodes, the subset for use in immobilizing a target, the
method comprising: a step for recalling a stored sequence of
entries, each entry identifying a respective subset of electrodes;
and a step for sequentially testing subsets in accordance with the
sequence of entries.
9. An immobilization device comprising: a signal source that
provides an immobilization signal; a plurality of electrodes; and a
circuit that selectively couples each of a multiplicity of subsets
of electrodes of the plurality of electrodes to the signal source
for delivery of the immobilization signal via a selected subset of
electrodes.
10. The device of claim 9 wherein the circuit: determines a
respective test result in response to coupling each subset of the
multiplicity to the signal source; and selects the selected subset
of electrodes in accordance with comparing the test result of the
selected subset to a limit.
11. The device of claim 9 wherein the immobilization signal
comprises a peak voltage less than an ionization voltage.
12. The device of claim 9 wherein the immobilization signal
comprises: a stage for determining the respective test result; and
a stage for immobilizing a target having tissue in series between
at least two electrodes of the selected subset of electrodes.
13. A projectile comprising the device of claim 9.
14. A system for immobilizing a target, the system comprising a
launch device and the projectile of claim 13.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of and claims
priority to U.S. application entitled "Systems and Methods Using an
Electrified Projectile" by Patrick W. Smioth, et al., filed Nov.
13, 2003, incorporated herein by reference; and claims priority
under 35 U.S.C. .sctn. 119(e) to copending U.S. application Ser.
No. 60/509,577 filed on Oct. 7, 2003 by Patrick Smith et al.,
incorporated herein by reference; and to copending U.S. application
Ser. No. 60/509,480 filed on Oct. 8, 2003 by Patrick Smith et al.,
incorporated herein by reference.
FIELD OF THE INVENTION
[0003] Embodiments of the present invention generally relate to
systems and methods for reducing mobility in a person or
animal.
BACKGROUND OF THE INVENTION
[0004] Weapons that deliver electrified projectiles have been used
for self defense and law enforcement. These weapons typically
deliver a stimulus signal through a target where the target is a
human being or an animal. One conventional class of such weapons
includes conducted energy weapons of the type described in U.S.
Pat. Nos. 3,803,463 and 4,253,132 to Cover. These weapons typically
fire projectiles toward the target so that electrodes carried by
the projectile make contact with the target, completing a circuit
that delivers a stimulus signal via tether wires through the
electrodes and through the target. Other conventional conducted
energy weapons omit the projectiles and deliver a stimulus signal
through electrodes placed in contact with the target when the
target is in close proximity to the weapon.
[0005] The stimulus signal may include a series of relatively high
voltage pulses known to cause pain in the target. At the time that
the stimulus signal is delivered, a high impedance gap (e.g., air
or clothing) may exist between electrodes and the target's
conductive tissue. Conventional stimulus signals include a
relatively high voltage (e.g., about 50,000 volts) signal to ionize
a pathway across such a gap of up to 2 inches. Consequently, the
stimulus signal may be conducted through the target's tissue
without penetration of the projectile into the tissue.
[0006] In some conventional conducted energy weapons, a relatively
higher energy waveform has been used. This waveform was developed
from studies using anesthetized pigs to measure the muscular
response of a mammalian subject to an energy weapon's stimulation.
Devices using the higher energy waveform are called
Electro-Muscular Disruption (EMD) devices and are of the type
generally described in U.S. patent application Ser. No. 10/016,082
to Patrick Smith, filed Dec. 12, 2001, incorporated herein by this
reference. An EMD waveform applied to an animal's skeletal muscle
typically causes that skeletal muscle to violently contract. The
EMD waveform apparently overrides the target's nervous system's
muscular control, causing involuntary lockup of the skeletal
muscle, and may result in complete immobilization of the
target.
[0007] Unfortunately, the relatively higher energy EMD waveform is
generally produced from a higher power capability energy source. In
one implementation, a handheld launch device includes 8 AA size
(1.5 volt nominal) batteries, a large capacity capacitor, and
transformers to generate a 26-watt EMD output in a tethered
projectile.
[0008] A two pulse waveform of the type described in U.S. patent
application Ser. No. 10/447,447 to Magne Nerheim filed Feb. 11,
2003, provides a relatively high voltage, lower amperage pulse (to
form an arc through a gap as discussed above) followed by a
relatively low voltage, higher amperage pulse (to stimulate the
target). Effects on skeletal muscles may be achieved with 80% less
power than used for the EMD waveform discussed above.
[0009] There exists a significant need for a more effective
stimulus signal for use in conducted energy weapons to immobilize a
human target without lasting injury or death. In the decade
preceding this application, annually over 30,000 people died of
bullet wounds in the United States. Further, thousands of police
officers are injured as a result of confrontations with non
compliant members of the general public each year. Even larger
numbers of these non-compliant subjects are injured in the process
of being taken into police custody. Without systems and methods for
delivering more effective stimulus signals, further improvements in
cost, reliability, range, and effectiveness cannot be realized for
conducted energy weapons. Applications for conducted energy weapons
will remain limited, hampering law enforcement and failing to
provide increased self defense to individuals.
SUMMARY OF THE INVENTION
[0010] An immobilization device, according to various aspects of
the present invention, includes three or more electrodes and a
signal generator selectively coupled to a first electrode, to a
second electrode, and to a third electrode. The signal generator
provides a test signal via the first electrode and the second
electrode to prompt movement of the target toward the third
electrode. The signal generator also provides a stimulus signal for
immobilization via the third electrode. The third electrode is
arranged to come into contact with the target as a consequence of
movement of the target.
[0011] A method for immobilizing a target, according to various
aspects of the present invention, includes in any order: (a)
providing a first electrode in contact with the target and a second
electrode in contact with the target; (b) providing a first signal
via the first electrode and the second electrode; (c) providing a
third electrode for coming into contact with the target as a
consequence of movement of the target in response to the first
signal; and (d) providing an immobilizing signal via the third
electrode.
[0012] A method, according to various aspects of the present
invention, for selecting a subset of electrodes from a plurality of
electrodes, the subset for use in immobilizing a target, includes
in any order: (a) recalling a stored sequence of entries, each
entry identifying a respective subset of electrodes; and (b)
sequentially testing subsets in accordance with the sequence of
entries.
[0013] An immobilization device, according to various aspects of
the present invention, includes a signal source that provides an
immobilization signal; a plurality of electrodes; and a circuit.
The circuit selectively couples each of a multiplicity of subsets
of electrodes of the plurality of electrodes to the signal source
for delivery of the immobilization signal via a selected subset of
electrodes.
[0014] Systems, devices, circuits and methods according to various
aspects of the present invention solve the problems discussed above
at least in part by more effectively immobilizing a target, by
reducing the risk of serious injury or death, and/or by
immobilizing for a period of time with an expenditure of energy
less than systems using techniques of the prior art.
BRIEF DESCRIPTION OF THE DRAWING
[0015] Embodiments of the present invention will now be further
described with reference to the drawing, wherein like designations
denote like elements, and:
[0016] FIG. 1 is a functional block diagram of a system that uses a
stimulus signal for immobilization according to various aspects of
the present invention;
[0017] FIG. 2 is a functional block diagram of an immobilization
device used in the system of FIG. 1;
[0018] FIG. 3 is a timing diagram for a stimulus signal provided by
the immobilization device of FIG. 2; and
[0019] FIG. 4 is a functional flow diagram for a process performed
by the immobilization device of FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] A system according to various aspects of the present
invention delivers a stimulus signal to an animal to immobilize the
animal. Immobilization is suitably temporary, for example, to
remove the animal from danger or to thwart actions by the animal
such as for applying more permanent restraints on mobility.
Electrodes may come into contact with the animal by the animal's
own action (e.g., motion of the animal toward an electrode), by
propelling the electrode toward the animal (e.g., electrodes being
part of an electrified projectile), by deployment mechanisms,
and/or by gravity. For example, system 100 of FIGS. 1-4 includes
launch device 102 and cartridge 104. Cartridge 104 includes one or
more projectiles 132, each having a waveform generator 136.
[0021] Launch device 102 includes power supply 112, aiming
apparatus 114, propulsion apparatus 116, and waveform controller
122. Propulsion apparatus 116 includes propulsion activator 118 and
propellant 120. In an alternate implementation, propellant 120 is
part of cartridge 104. Waveform controller 122 may be omitted with
commensurate simplification of waveform generator 136, discussed
below.
[0022] Any conventional materials and technology may be employed in
the manufacture and operation of launch device 102. For example,
power supply 112 may include one or more rechargeable batteries,
aiming apparatus 114 may include a laser gun sight, propulsion
activator 118 may include a mechanical trigger similar in some
respects to the trigger of a hand gun, and propellant 120 may
include compressed nitrogen gas. In one implementation, launch
device is handheld and operable in a manner similar to a
conventional hand gun. In operation, cartridge 104 is mounted on or
in launch device 102, manual operation by the user causes the
projectile bearing electrodes to be propelled away from launch
device 102 and toward a target (e.g., an animal such as a human),
and after the electrodes become electrically coupled to the target,
a stimulus signal is delivered through a portion of the tissue of
the target.
[0023] Projectile 132 may be tethered to launch device 102 and
suitable circuitry in launch device 102 (not shown) using any
conventional technology for purposes of providing substitute or
auxiliary power to power source 134; triggering, retriggering, or
controlling waveform generator 136; activating, reactivating, or
controlling deployment; and/or receiving signals at launch device
102 provided from electrodes 142 in cooperation with
instrumentation in projectile 132 (not shown).
[0024] A waveform controller includes a wireless communication
interface and a user interface. The communication interface may
include a radio or an infrared transceiver. The user interface may
include a keypad and flat panel display. For example, waveform
controller 122 forms and maintains a link by radio communication
with waveform generator 136 for control and telemetry using
conventional signaling and data communication protocols. Waveform
controller 122 includes an operator interface capable of displaying
status to the user of system 100 and capable of issuing controls
(e.g., commands, messages, or signals) to waveform generator 136
automatically or as desired by the user. Controls serve to control
any aspect and/or collect data from any circuit of projectile 132.
Controls may affect time and amplitude characteristics of the
stimulus signal including overall start, restart, and stop
functions. Telemetry may include feedback control of any function
of waveform generator 136 or other instrumentation in projectile
132 implemented with conventional technology (not shown). Status
may include any characteristics of the stimulus signal and stimulus
signal delivery circuit.
[0025] Cartridge 104 includes projectile 132 having power source
134, waveform generator 136, and electrode deployment apparatus
138. Electrode deployment apparatus 138 includes deployment
activator 140 and one or more electrodes 142. Power source 134 may
include any conventional battery selected for relatively high
energy output to volume ratio. Waveform generator 136 receives
power from power source 134 and generates a stimulus signal
according to various aspects of the present invention. The stimulus
signal is delivered into a circuit that is completed by a path
through the target via electrodes 142. Power source 134, waveform
generator 136, and electrodes 142 cooperate to form a stimulus
signal delivery circuit that may further include one or more
additional electrodes not deployed by deployment activator 142
(e.g., placed by impact of projectile 132).
[0026] Projectile 132 may include a body having compartments or
other structures for mounting power source 134, a circuit assembly
for waveform generator 136, and electrode deployment apparatus 138.
The body may be formed in a conventional shape for ballistics
(e.g., a wetted aerodynamic form).
[0027] An electrode deployment apparatus includes any mechanism
that moves electrodes from a stowed configuration to a deployed
configuration. For example, in an implementation where electrodes
142 are part of a projectile propelled through the atmosphere to
the target, a stowed configuration provides aerodynamic stability
for accurate travel of the projectile. A deployed configuration
completes a stimulus signal delivery circuit directly via impaling
the tissue or indirectly via an arc into the tissue. A separation
of about 7 inches has been found to be more effective than a
separation of about 1.5 inches; and, longer separations may also be
suitable such as an electrode in the thigh and another in the hand.
When the electrodes are further apart, the stimulus signal
apparently passes through more tissue, creating more effective
stimulation.
[0028] According to various aspects of the present invention,
deployment of electrodes is activated after contact is made by
projectile 132 and the target. Contact may be determined by a
change in orientation of the deployment activator; a change in
position of the deployment activator with respect to the projectile
body; a change in direction, velocity, or acceleration of the
deployment activator; and/or a change in conductivity between
electrodes (e.g., 142 or electrodes placed by impact of projectile
132 and the target). A deployment activator 140 that detects impact
by mechanical characteristics and deploys electrodes by the release
or redirection of mechanical energy is preferred for low cost
projectiles.
[0029] Deployment of electrodes, according to various aspects of
the present invention, may be facilitated by behavior of the
target. For example, one or more closely spaced electrodes at the
front of the projectile may attach to a target to excite a painful
reaction in the target. One or more electrodes may be exposed and
suitably directed (e.g., away from the target). Exposure may be
either during flight or after impact. Pain in the target may be
caused by the barb of the electrode stuck into the target's flesh
or, if there are two closely space electrodes, delivery of a
stimulus signal between the closely spaced electrodes. While these
electrodes may be too close together for suitable immobilization,
the stimulus signal may create sufficient pain and disorientation.
A typical response behavior to pain is to grab at the perceived
cause of pain with the hands (or mouth, in the case of an animal)
in an attempt to remove the electrodes. This so called "hand trap"
approach uses this typical response behavior to implant the one or
more exposed electrodes into the hand (or mouth) of the target. By
grabbing at the projectile, the one or more exposed electrodes
impale the target's hand (or mouth). The exposed electrodes in the
hand (or mouth) of the target are generally well spaced apart from
other electrodes so that stimulation between another electrode and
an exposed electrode may allow suitable immobilization.
[0030] In an alternate system implementation, launch device 102,
cartridge 104, and projectile 132 are omitted; and power source
134, waveform generator 136, and electrode deployment apparatus 138
are formed as an immobilization device 150 adapted for other
conventional forms of placement on or in the vicinity of the
target. In another alternate implementation, deployment apparatus
138 is omitted and electrodes 142 are placed by target behavior
and/or gravity. Immobilization device 150 may be packaged using
conventional technology for personal security (e.g., planting in a
human target's clothing or in an animal's hide for future
activation), facility security (e.g., providing time for
surveillance cameras, equipment shutdown, or emergency response),
or military purposes (e.g., land mine).
[0031] Projectile 132 may be lethal or non-lethal. In alternate
implementations, projectile 132 includes any conventional
technology for administering deadly force.
[0032] Immobilization as discussed herein includes any restraint of
voluntary motion by the target. For example, immobilization may
include causing pain or interfering with normal muscle function.
Immobilization need not include all motion or all muscles of the
target. Preferably, involuntary muscle functions (e.g., for
circulation and respiration) are not disturbed. In variations where
placement of electrodes is regional, loss of function of one or
more skeletal muscles accomplishes suitable immobilization. In
another implementation, suitable intensity of pain is caused to
upset the target's ability to complete a motor task, thereby
incapacitating and disabling the target.
[0033] Alternate implementations of launch device 102 may include
or substitute conventionally available weapons (e.g., firearms,
grenade launchers, vehicle mounted artillery). Projectile 132 may
be delivered via an explosive charge 120 (e.g., gunpowder, black
powder). Projectile 132 may alternatively be propelled via a
discharge of compressed gas (e.g., nitrogen or carbon dioxide)
and/or a rapid release of pressure (e.g., spring force, or force
created by a chemical reaction such as a reaction of the type used
in automobile air-bag deployment).
[0034] A waveform generator, according to various aspects of the
present invention, may, in any order perform one or more of the
following operations: select electrodes for use in a stimulus
signal delivery circuit, ionize air in a gap between the electrode
and the target, provide an initial stimulus signal, provide
alternate stimulus signals, and respond to operator input to
control any of the aforementioned operations. In one
implementation, a large portion of these operations are controlled
by firmware performed by a processor to permit miniaturization of
the waveform generator, reduce costs, and improve reliability. For
example, waveform generator 200 of FIG. 2 may be used as waveform
generator 136 discussed above. Waveform generator 200 includes low
voltage power supply 204, high voltage power supply 206, switches
208, processor circuit 220, and transceiver 240.
[0035] The low voltage power supply receives a DC voltage from
power source 134 and provides other DC voltages for operation of
waveform generator 200. For example, low voltage power supply 204
may include a conventional switching power supply circuit (e.g.,
LTC3401 marketed by Linear Technology) to receive 1.5 volts from a
battery of source 134 and supply 5 volts and 3.3 volts DC.
[0036] The high voltage power supply receives an unregulated DC
voltage from a low voltage power supply and provides a pulsed,
relatively high voltage waveform as stimulus signal VP. For
example, high voltage power supply 206 includes switching power
supply 232, transformer 234, rectifier 236, and storage capacitor
C12 all of conventional technology. In one implementation,
switching power supply 232 comprising a conventional circuit (e.g.,
LTC 1871 marketed by Linear Technology) receives 5 volts DC from
low voltage power supply 204 and provides a relatively low AC
voltage for transformer 234. A feedback control signal into
switching power supply 232 assures that the peak voltage of signal
VP does not exceed a limit (e.g., 500 volts). Transformer 234 steps
up the relatively low AC voltage on its primary winding to a
relatively high AC voltage on each of two secondary windings (e.g.,
500 volts). Rectifier 236 provides DC current for charging
capacitor C12.
[0037] Switches 208 form stimulus signal VP across electrode(s) by
conducting for a brief period of time to form each pulse; followed
by opening. The discharge voltage available from capacitor C12
decreases during the pulse duration. When switches 208 are open,
capacitor C12 may be recharged to provide the same discharge
voltage for each pulse.
[0038] Processor circuit 220 includes a conventional programmable
controller circuit having a microprocessor, memory, and analog to
digital converter programmed according to various aspects of the
present invention, to perform methods discussed below.
[0039] A projectile-based transceiver communicates with a waveform
controller as discussed above. For example, transceiver 240
includes a radio frequency (e.g., about 450 MHz) transmitter and
receiver adapted for data communication between projectile 132 and
launch device 102 at any time. A communication link between 136 and
122 may be established in any suitable configuration of projectile
132 depending for example on placement and design of radiators and
pickups suitable for the communication link (e.g., antennas or
infrared devices). In one implementation projectile 132 operates in
four configurations: (1) a stowed configuration, where aerodynamic
fins and deployable electrodes are in storage locations and
orientations; (2) an in flight configuration, where aerodynamic
fins are in position extended away from projectile 132; (3) an
impact configuration after contact with the target; and (4) an
electrode deployed configuration.
[0040] A stimulus signal includes any signal delivered via
electrodes to establish or maintain a stimulus signal delivery
circuit through the target, and/or to immobilize the target.
According to various aspects of the present invention, these
purposes are accomplished with a signal having a plurality of
stages. Each stage comprises a period of time during which one or
more waveforms are consecutively delivered via a waveform generator
and electrodes coupled to the waveform generator. Stages from which
a complete waveform, according to various aspects of the present
invention may be constructed include in any order: (a) a path
formation stage for ionizing an air gap that may be in series with
the electrode to the targets tissue; (b) a path testing stage for
measuring an electrical characteristic of the stimulus signal
delivery circuit (e.g., whether or not an air gap exists in series
with the target's tissue); (c) a strike stage for immobilizing the
target; (d) a hold stage for discouraging further motion by the
target; and (e) a rest stage for permitting limited mobility by the
target (e.g., to allow the target to catch a breath).
[0041] An example of signal characteristics for each stage is
described in FIG. 3. In FIG. 3, two stages of a stimulus signal are
attributed to path management and three stages are attributed to
target management. The waveform shape of each stage may have
positive amplitude (as shown), inverse amplitude, or alternate
between positive and inverse amplitudes in repetitions of the same
stage. Path management stages include a path formation stage and a
path testing stage as discussed above.
[0042] In the path formation stage, a waveform shape may include an
initial peak (voltage or current), subsequent lesser peaks
alternating in polarity, and a decaying amplitude tail. The initial
peak voltage may exceed the ionization potential for an air gap of
expected length (e.g., about 50 Kvolts, preferably about 10
Kvolts). In one implementation, the waveform shape is formed as a
decaying oscillation from a conventional resonant circuit. One
waveform shape having one or more peaks may be sufficient to ionize
a path crossing a gap (e.g., air). Repetition of applying such a
waveform shape may follow a path testing stage (or monitoring
concurrent with another stage) that concludes that ionization is
needed and is to be attempted again (e.g., prior attempt failed, or
ionized air is disrupted).
[0043] In a path testing stage, a voltage waveform is sourced and
impressed across a pair of electrodes to determine whether the path
has one or more electrical characteristics sufficient for entry
into a path formation, strike, or hold stage. Path impedance may be
determined by any conventional technique, for instance, monitoring
an initial voltage and a final voltage across a capacitor that is
coupled for a predetermined period of time to supply current into
electrodes. In one implementation, the shape of the voltage pulse
is substantially rectangular having a peak amplitude of about 450
volts, and having a duration of about 10 microseconds. A path may
be tested several times in succession to form an average test
result, for instance from one to three voltage pulses, as discussed
above. Testing of all combinations of electrodes may be
accomplished in about one millisecond. Results of path testing may
be used to select a pair of electrodes to use for a subsequent path
formation, strike, or hold stage. Selection may be made without
completing tests on all possible pairs of electrodes, for instance,
when electrode pairs are tested in a sequence from most preferred
to least preferred.
[0044] In a strike stage, a voltage waveform is sourced and
impressed across a pair of electrodes. Typically this waveform is
sufficient to interfere with voluntary control of the target's
skeletal muscles, particularly the muscles of the thighs and/or
calves. In another implementation, use of the hands, feet, legs and
arms are included in the effected immobilization. The pair may be
as selected during a test stage; or as prepared for conduction by a
path formation stage. According to various aspects of the present
invention, the shape of the waveform used in a strike stage
includes a pulse with decreasing amplitude (e.g., a trapezoid
shape). In one implementation, the shape of the waveform is
generated from a capacitor discharge between an initial voltage and
a termination voltage.
[0045] The initial voltage may be a relatively high voltage for
paths that include ionization to be maintained or a relatively low
voltage for paths that do not include ionization. The initial
voltage may correspond to a stimulus peak voltage (SPV) as in FIG.
3 (e.g., at about a skeletal muscle nerve action potential). The
SPV may be essentially the initial voltage for a fast rise time
waveform. The SPV following ionization may be from about 3 Kvolts
to about 6 Kvolts, preferably about 5 Kvolts. The SPV without
ionization may be from about 100 to about 600 volts, preferably
from about 350 volts to about 500 volts, most preferably about 400
volts.
[0046] The termination voltage may be determined to deliver a
predetermined charge per pulse. Charge per pulse minimum may be
designed to assure continuous muscle contraction as opposed to
discontinuous muscle twitches. Continuous muscle contraction has
been observed in human targets where charge per pulse is above
about 15 microcoulombs. A minimum of about 50 microcoulombs is used
in one implementation. A minimum of 85 microcoulombs is preferred,
though higher energy expenditure accompanies the higher minimum
charge per pulse.
[0047] Charge per pulse maximum may be determined to avoid cardiac
fibrillation in the target. For human targets, fibrillation has
been observed at 1355 microcoulombs per pulse and higher. The value
1355 is an average observed over a relatively wide range of pulse
repetition rates (e.g., from about 5 to 50 pulses per second), over
a relatively wide range of pulse durations consistent with
variation in resistance of the target (e.g., from about 10 to about
1000 microseconds), and over a relatively wide range of peak
voltages per pulse (e.g., from about 50 to about 1000 volts). A
maximum of 500 microcoulombs significantly reduces the risk of
fibrillation while a lower maximum (e.g., about 100 microcoulombs)
is preferred to conserve energy expenditure.
[0048] Pulse duration is preferably dictated by delivery of charge
as discussed above. Pulse duration according to various aspects of
the present invention is generally longer than conventional systems
that use peak pulse voltages higher than the ionization potential
of air. Pulse duration may be in the range from about 20 to about
500 microseconds, preferably in the range from about 30 to about
200 microseconds, and most preferably in the range from about 30 to
about 100 microseconds.
[0049] By conserving energy expenditure per pulse, longer durations
of immobilization may be effected and smaller, lighter power
sources may be used (e.g., in a projectile comprising a battery).
In one implementation, a AAAA size battery is included in a
projectile to deliver about 1 watt of power during target
management which may extend to about 10 minutes. In such an
embodiment, a suitable range of charge per pulse may be from about
50 to about 150 microcoulombs.
[0050] Initial and termination voltages may be designed to deliver
the charge per pulse in a pulse having a duration in a range from
about 30 microseconds to about 210 microseconds (e.g., for about 50
to 100 microcoulombs). A discharge duration sufficient to deliver a
suitable charge per pulse depends in part on resistance between
electrodes at the target. For example, a one RC time constant
discharge of about 100 microseconds may correspond to a capacitance
of about 1.75 microfarads and a resistance of about 60 ohms. An
initial voltage of 100 volts discharged to 50 volts may provide
87.5 microcoulombs from the 1.75 microfarad capacitor.
[0051] A termination voltage may be calculated to ensure delivery
of a predetermined charge. For example, an initial value may be
observed corresponding to the voltage across a capacitor. As the
capacitor discharges delivering charge into the target, the
observed value may decrease. A termination value may be calculated
based on the initial value and the desired charge to be delivered
per pulse. While discharging, the value may be monitored. When the
termination value is observed, further discharging may be limited
(or discontinued) in any conventional manner. In an alternate
implementation, delivered current is integrated to provide a
measure of charge delivered. The monitored measurement reaching a
limit value may be used to limit (or discontinue) further delivery
of charge.
[0052] Pulse durations in alternate implementations may be
considerably longer than 100 microseconds, for example, up to 1000
microseconds. Longer pulse durations increase a risk of cardiac
fibrillation. In one implementation, consecutive strike pulses
alternate in polarity to dissipate charge which may collect in the
target to adversely affect the target's heart.
[0053] During the strike stage, pulses are delivered at a rate of
about 5 to about 50 pulses per second, preferably about 20 pulses
per second. The strike stage continues from the rising edge of the
first pulse to the falling edge of the last pulse of the stage for
from 1 to 5 seconds, preferably about 2 seconds.
[0054] In a hold stage, a voltage waveform is sourced and impressed
across a pair of electrodes. Typically this waveform is sufficient
to discourage mobility and/or continue immobilization to an extent
somewhat less than the strike stage. A hold stage generally demands
less power than a strike stage. Use of hold stages intermixed
between strike stages permit the immobilization effect to continue
as a fixed power source is depleted (e.g., battery power) for a
time longer than if the strike stage were continued without hold
stages. The stimulus signal of a hold stage may primarily interfere
with voluntary control of the target's skeletal muscles as
discussed above or primarily cause pain and/or disorientation. The
pair of electrodes may be the same or different than used in a
preceding path formation, path testing, or strike stage, preferably
the same as an immediately preceding strike stage. According to
various aspects of the present invention, the shape of the waveform
used in a hold stage includes a pulse with decreasing amplitude
(e.g., a trapezoid shape) and initial voltage (SPV) as discussed
above with reference to the strike stage. The termination voltage
may be determined to deliver a predetermined charge per pulse less
than the pulse used in the strike stage (e.g., from 30 to 100
microcoulombs). During the hold stage, pulses may be delivered at a
rate of about 5 to 15 pulses per second, preferably about 10 pulses
per second. The strike stage continues from the rising edge of the
first pulse to the falling edge of the last pulse of the stage for
from about 20 to about 40 seconds (e.g., about 28 seconds).
[0055] A rest stage is a stage intended to improve the personal
safety of the target and/or the operator of the system. In one
implementation, the rest stage does not include any stimulus
signal. Consequently, use of a rest stage conserves battery power
in a manner similar to that discussed above with reference to the
hold stage. Safety of a target may be improved by reducing the
likelihood that the target enters a relatively high risk physical
or emotional condition. High risk physical conditions include risk
of loss of involuntary muscle control (e.g., for circulation or
respiration), risk of convulsions, spasms, or fits associated with
a nervous disorder (e.g., epilepsy, or narcotics overdose). High
risk emotional conditions include risk of irrational behavior such
as behavior springing from a fear of immediate death or suicidal
behavior. Use of a rest stage may reduce a risk of damage to the
long term health of the target (e.g., minimize scar tissue
formation and/or unwarranted trauma). A rest stage may continue for
from 1 to 5 seconds, preferably 2 seconds.
[0056] In one implementation, a strike stage is followed by a
repeating series of alternating hold stages and rest stages.
[0057] In any of the deployed electrode configurations discussed
above, the stimulation signal may be switched between various
electrodes so that not all electrodes are active at any particular
time. Accordingly, a method for applying a stimulus signal to a
plurality of electrodes includes, in any order: (a) selecting a
pair of electrodes; (b) applying the stimulus signal to the
selected pair; (c) monitoring the energy (or charge) delivered into
the target; (d) if the delivered energy (or charge) is less than a
limit, conclude that at least one of the selected electrodes is not
sufficiently coupled to the target to form a stimulus signal
delivery circuit; and (e) repeating the selecting, applying, and
monitoring until a predetermined total stimulus (energy and/or
charge) is delivered. A microprocessor performing such a method may
identify suitable electrodes in less than a millisecond such that
the time to select the electrodes is not perceived by the
target.
[0058] A waveform generator, according to various aspects of the
present invention may perform a method for delivering a stimulus
signal that includes selecting a path, preparing the path for the
stimulus signal, and repeatedly providing the stimulus signal for a
sequence of effects including in any order: a comparatively highly
immobilizing effect (e.g., a strike stage as discussed above), a
comparatively lower immobilizing effect (e.g., a hold stage as
discussed above), and a comparatively lowest immobilizing effect
(e.g., a rest stage as discussed above). For example, method 400 of
FIG. 4 is implemented as instructions stored in a memory device
(e.g., stored and/or conveyed by any conventional disk media and/or
semiconductor circuit) and installed to be performed by a processor
(e.g., in read only memory of processor circuit 220).
[0059] Method 400 begins with a path testing stage as discussed
above comprising a loop (402-408) for determining an acceptable or
preferred electrode pair. Because the projectile may include
numerous electrodes, any subset of electrodes may be selected for
application of a stimulus signal. Data stored in a memory
accessible to the processor of circuit 220 may include a list of
electrode subsets (e.g., pairs), preferably an ordered list from
most preferred for maximum immobilization effect to least
preferred. In one implementation, the ordered list indicates one
preference for one subset of electrodes to be used in all stages
discussed above. In another implementation, the list is ordered to
convey a preference for a respective electrode subset for each of
more than one stage. Method 400 uses one list to express suitable
electrode preferences. Alternate implementations include more than
one list and/or more than one loop (402-408) (e.g., a list and/or
loop for each stage). In another alternate implementation a list
includes duplicate entries of the same subset so that the subset is
tested before and after intervening test or stimulus signals.
[0060] According to method 400, after path management, processor
220 performs target management. Path management may include path
formation, as discussed above. Target management may be interrupted
to perform path management as discussed below (434). For target
management, processor 220 provides the stimulus signal in a
sequence of stages as discussed above. In one implementation a
sequence of stages is effected by performing a loop (424-444).
[0061] For each (424) stage of a predefined stage sequence, a loop
(426-442) is performed to provide a suitable stimulus signal. Prior
to entry of the inner loop (426-442), a stage is identified. The
stage sequence may include one strike stage, followed by
alternating hold and rest stages as discussed above.
[0062] For the duration of the identified stage (426), processor
220 charges capacitors (428) (e.g., C12 used for signal VP) until
charge sufficient for delivery (e.g., 100 microcoulombs) is
available or charging is interrupted by a demand to provide a pulse
(e.g., operator command via transceiver 240, a result of electrode
testing, or lapse of a timer). Processor 220 then forms a pulse
(e.g., a strike stage pulse or hold stage pulse) at the value of
SPV set as discussed above (422 or 414). Processor 220 meters
delivery of charge (432), in one implementation, by observing the
voltage (e.g., VC) of the storage capacitors decrease (436) until
such voltage is at or beyond a limit voltage (e.g., about 228
volts). The selection of a suitable limit voltage may follow the
well known relationship: .DELTA.Q=C.DELTA.V where Q is charge in
coulombs; C is capacitance in farads; and V is voltage across the
capacitor in volts.
[0063] During metering of charge delivery, processor 220 may detect
(434) that the path in use for the identified stage has failed. On
failure, processor 220 quits the identified stage, quits the
identified stage sequence, and returns (402) to path testing as
discussed above.
[0064] When the quantity of charge suitable for the identified
stage has been delivered (436), the pulse (e.g., signal VP) is
ended (440). The voltage supplied after the pulse is ended may be
zero (e.g., open circuit at least one of the identified electrodes)
or a nominal voltage (e.g., sufficient to maintain ionization).
[0065] If the identified stage is not complete, then processing
continues at the top of the inner loop (426). The identified stage
may not be complete when a duration of the stage has not lapsed; or
a predetermined quantity of pulses has not been delivered.
Otherwise, processor 220 identifies (444) the next stage in the
sequence of stages and processing continues in the outer loop
(424). The outer loop may repeat a stage sequence (as shown) until
the power source for waveform generator is fully depleted.
[0066] For each (402) listed electrode subset, processor 220
applies (404) a test voltage across an identified electrode subset.
In one implementation, processor 220 applies a comparatively low
test voltage (e.g., about 500 volts) to determine an impedance of
the stimulus signal delivery circuit that includes the identified
electrodes. Impedance may be determined by evaluating current,
charge, or voltage. For instance, processor 220 may observe a
change in voltage of a signal (e.g., VC) corresponding to the
voltage across the a capacitor (e.g., C12) used to supply the test
voltage. If observed change in voltage (e.g., peak or average
absolute value) exceeds a limit, the identified electrodes are
deemed suitable and the stimulus peak voltage is set to 450 volts.
Otherwise, if not at the end of the list, another subset is
identified (408) and the loop continues (402).
[0067] In another implementation, processor 220 applies a
comparatively low test voltage (e.g., about 500 volts) with
delivery of a suitable charge (e.g., from about 20 to about 50
microcoulombs) to attract movement of the target toward an
electrode. For example, movement may result in impaling the
target's hand on a rear facing electrode thereby establishing a
preferred circuit through a relatively long path through the
target's tissue. In one implementation, the rear facing electrode
is close in proximity to electrodes of the subset and is also a
member of the subset. Alternatively, the rear facing electrode may
be relatively distant from other electrodes of the set and/or not a
member of the subset.
[0068] The test signal used in one implementation has a pulse
amplitude and a pulse width within the ranges used for stimulus
signals discussed herein. One or more pulses constitute a test of
one subset. In alternate implementations, the test signal is
continuously applied during the test of a subset and test duration
for each subset corresponds to the pulse width within the range
used for stimulus signals discussed herein.
[0069] If at the end of the list no pair is found acceptable,
processor 220 identifies a pair of electrodes for a path formation
stage as discussed above. Processor 220 applies (412) an ionization
voltage to the electrodes in any conventional manner. Presuming
ionization occurred, subsequent strike stages and hold stages may
use a stimulus peak voltage to maintain ionization. Consequently,
SPV is set (414) to 3 Kvolts.
[0070] The foregoing description discusses preferred embodiments of
the present invention which may be changed or modified without
departing from the scope of the present invention as defined in the
claims. While for the sake of clarity of description, several
specific embodiments of the invention have been described, the
scope of the invention is intended to be measured by the claims as
set forth below.
* * * * *